1. Field of the Invention
The present invention relates to an improved toroidal continuously variable transmission use for power transmission of a vehicle, particularly to achieve a structure that enables high transmission efficiency by smoothly shifting power roller in respect to a trunnion.
2. Description of Related Art
Examples of a toroidal continuously variable transmission used for a vehicle are disclosed in various publications, for example, Japanese Patent Unexamined Publications JP-A-03-74667 and JP-A-2001-165262 and Non Patent Documents “Best Car Supplement Volume Entitled Red Badge Series 245/Book Presenting Automotive Latest Mechanisms” pages 92-93 on Dec. 20, 2001, by Aoyama Motto in Sunsuisha Co. Ltd./Kodansha co. Ltd., and “Toroidal CVT” on Jul. 13, 2000, by Tanaka Hirohisa in Corona Publishing Co. Ltd., and some of which are known and in use. FIG. 70 shows a basic configuration of a toroidal continuously variable transmission that is known in the art. The configuration in the related art is first simply described. A pair of input discs 1a, 1b is coaxially and synchronously rotatably supported by an input rotary shaft 2, facing input-side inner faces 3 of toroidal curves (arc recess in the cross-section).
An output cylinder 5 with an output gear 4 fixed around the outside of the intermediate portion is rotatably supported at the intermediate portion of the input rotary shaft 2. An Output disc 6 is synchronously rotatably supported at both ends of the output cylinder 5 by a spline. Further, output-side inner faces 7 of toroidal curves of the output discs 6 face both of the input-side inner faces 3.
Two power rollers 8 having spherical convex surfaces are disposed (in the cavity) between the input-side and output-side inner faces 3, 7, respectively, around the input rotary shaft 2. The power rollers 8, 8 are supported on the inner surface of corresponding trunnions 9, 9 by a plurality of rolling bearings and support shafts 10 with eccentric upper and base halves such that they can rotate with the upper halves of the support shafts 10 and swing around the base halves of the support shafts 10.
Further, each of the trunnions 9 is disposed rotatably about tilt rotary shaft coaxially disposed at both longitudinal ends (in the direction vertical to the surface of FIG. 70) of the trunnion 9. The trunnion 9 swings (inclines) by being displaced in axial direction of the tilt rotary shaft by using a hydraulic actuator. In change of speed, the trunnions 9 are moved axially of the tilt rotary shafts by pressurized fluid supplied from the actuators. As a result, force tangentially exerting at the contact portions (traction portions) of the input-/output-side inner faces 3, 7 and the power rollers 8 changes in direction (sideslip appears), so that the trunnions 9 swing around the tilt rotary shafts.
To start the above-mentioned toroidal continuously variable transmission, an input disc 1a at one side (the left in FIG. 70) is rotated through a loading cam type loader 12 by a driving shaft 11. Accordingly, the input discs 1a, 1b supported at both ends of the input rotary shaft 2 are pressed close, rotating synchronously. The rotation is transferred through the power rollers 8 to the output discs 6 and outputted through the output gear 4.
In changing the rotational speed ratio of the input rotary shaft 2 and the output gear 4, in order to decelerate the input rotary shaft 2 and the output gear 4, the trunnions 9 swing to the position shown in FIG. 70 such that the outsides of the power rollers 8 contact with the center portions of the input-side inner faces 3 of the input discs 1a, 1b and the outer portions of the output-side inner faces 7 of the output discs 6. On the contrary, in acceleration, the trunnions 9 swing reverse to the position of FIG. 70 such that the outsides of the power rollers 8 contact with the outer portions of the input-side inner faces 3 of the input discs 1a, 1b and the center portions of the output-side inner faces 7 of the output discs 6. Intermediate speed ratio (transmission ratio) of the input rotary shaft 2 and the output gear 4 by positioning the trunnions 9 to half the swing angle.
When the toroidal continuously variable transmission is in operation, the members for power transmission, i.e. the input discs and output disc 1a, 1b, 6 and the power rollers 8 are elastically deformed by the pressing force (thrust) of the loader 12. The discs 1a, 1b, 6 are axially moved with the elastic deformation. Further, the pressing force of the loader 12 increases in accordance with increase in torque transferred by the toroidal continuously variable transmission and the amount of elastic deformation of the members increases correspondingly. Therefore, a mechanism for moving the power rollers 8 axially of the discs 1a, 1b, 6 in respect to the trunnions 9 regardless of changes in torque is required to appropriately maintain the contact of the input-side and output-side inner faces 3, 7 and the outsides of the power rollers 8. According to a first configuration of the related art shown in FIG. 70, the power rollers 8 are axially moved by swing the front halves of the support shafts 10 supporting the corresponding power rollers 8 about the base halves.
On the other hand, a toroidal continuously variable transmission is disclosed in German Patent Unexamined Publication DE 10 246 432 in which transmission ratio is changed and power rollers are moved axially of each disc by individual mechanisms. The above second toroidal continuously variable transmission in the related art has a transmission configuration shown in FIGS. 71 and 72. According to the second configuration shown in FIGS. 71 and 72, a swing frame 13 is mounted swingably about an input rotary shaft 2 around the input rotary shaft 2 between input and output discs 1, 6. Three trunnions 9a, 9a, 9a rotatably supporting power rollers 8a are supported only swingably about tilt rotary shafts 15 disposed at both ends between support plates 14 provided radial outer ends of the swing frame 13. The trunnions 9a, different from the configuration shown in FIG. 70, are not moved axially of the tilt rotary shafts 15 in respect to the swing frame 13. With the above configuration, the central extension lines a of the power rollers 8a cross each other at the central axis β of the discs 1, 6.
Of the tilt rotary shafts 15, sector gears 16, 16a are fixed to the tilt rotary shaft 15, exclusive of the two tilt rotary shafts 15 at the upper part in FIGS. 71 and 72. The sector gears 16, 16a that are circumferentially adjacent for the trunnions 9a are engaged. Accordingly, the trunnions 9a are inclined at the same angle in the same direction about the direction for changing transmission ratio. A sector gear 16a of the sector gears 16, 16a (right lower one in FIGS. 71 and 72) swings with respect to the tilt rotary shaft 15 fixing the sector gear 16a by a cam mechanism 17 and actuator 18.
The cam mechanism 17 consists of a cam follower 19 supported to the sector gear 16a and a cam member 21 fixed to the inner face of a housing 20 that houses the toroidal continuously variable transmission. The cam follower 19 is engaged with a cam groove 22 formed on the cam member 21. On the other hand, the actuator 18, a double-acting hydraulic actuator, transfers movement of a pin engaged with a long hole formed in a piston 23 through a connecting bracket 25 to the swing frame 13 and the swing frame 13 swings with respect to the input rotary shaft 2. The swing frame 13 swinging changes the positional relationship of the cam groove 22 and the cam follower 19 supported to the sector gear 16a and the sector gear 16a correspondingly swings with respect to the tilt rotary shaft 15. Further, the motion of the sector gear 16a is transferred to the trunnions 9a through the other sector gears 16. Consequently, the power rollers 8a supported to the inner side of the trunnions 9a swing at the same angel in the same direction in respect to the direction for changing the transmission ratio of the input and output discs 1, 6 and the transmission ratio is controlled to the desired value.
According to the configuration disclosed in DE 10 246 432 A1, in the relative positional relationship with the swing frame 13, the power rollers 8a in transmission swing only vertical to the surface of FIG. 72. In other words, the power rollers 8a are not moved axially of the tilt rotary shafts 15 (perpendicular to the extension lines α) in respect to the swing frame 13 for transmission (although they may be moved with the swing frame 13 in the rotational direction or opposite of the input rotary shaft 2). Further, the swing frame 13 is supported swingably only to a predetermined angle for transmission between the input and output discs 1, 6 and not moved axially of the discs 1, 6 (vertically to the surface of FIG. 72). Accordingly, the trunnions 9a do not move axially of the discs 1, 6.
On the other hand, when the toroidal continuously variable transmission is in operation, the members 1, 6, 8a are elastically deformed by additional force for ensuring surface pressure at the rotational contact portion (traction portion) between the inner surface 3, 7 of the discs 1, 6 and the outsides of the power rollers 8a. The power rollers 8a of them are moved vertical to the surface of FIG. 72. According to the configuration described in relation to FIG. 70, the power rollers 8 can be moved by elastic deformation of each member by swingably supporting them in respect to the trunnions 9 with the support shafts 10 (eccentric shafts) that make the base and front halves eccentric. However, according to the configuration shown in FIGS. 71 and 72, the power rollers 8a cannot swing by one eccentric shaft.
This is because, though the amount is a little, the power rollers 8a are moved in axial direction of the tilt rotary shafts 15 (perpendicular to the extension lines α) by motion along the arc having a rotational radius of the eccentric amount when the power rollers 8a swing by one eccentric shaft. As described in relation to the configuration shown in FIG. 70, side-slip appears at the traction portion when the power rollers 8a are moved axially of the tilt rotary shafts 15 and force is applied to the trunnions 9a through the power rollers 8a in the swing direction about the tilt rotary shafts 15 (the direction for changing the transmission ratio). The force is generated even at movement of 0.1 to 0.2. It is not preferable for the toroidal continuously variable transmission to operate under the side-slip and applied force. In detail, the side-slip results in reduction of transmission efficiency and durability and the force results in increase in the force to change the transmission ratio substantially required.
Accordingly, according to the configuration disclosed in DE 10 246 432 A1, the power rollers 8a are moved only axially of the input and output discs 1, 6 (vertical to the surface of FIG. 72) by elastic deformation of the members 1, 6, 8a, using the configurations shown in FIGS. 73 to 75. Used in the configurations, a support shaft 10a that rotatably supports the power roller 8a in respect to the trunnion 9a has an eccentric base 26 and support shaft portion 27, A circular recess 28 is centrally formed on the inner surface of the trunnion 9a. A cylindrical crank member 29 (thick disc) is engaged with the circular recess 28. Further, at a portion of the crank member 29, a circular hole 30 is formed at the outside from the center of the crank member 29. The eccentric amount δ2 between the central axes X29 and X30 of the crank member 29 and circular hole 30 is the same as the eccentric amount δ1 between the central axes X26 and X27 of the base portion 26 and the support shaft portion 27 (δ2=δ1). Accordingly, the base portion 26 is swingably engaged with the circular hole 30 without rattling. Therefore, the central axis X26 of the base portion 26 is arranged in a line with the central axis X30 of the circular hole 30.
At a portion of the trunnion 9a, a elongated hole for engaging that is long in axial direction of the tilt rotary shaft 15 is formed at the corner under the circular recess 28, communicating the outside of the trunnion 9a with the bottom of the circular recess 28. In the support shaft 10a, a guide rod 32 protruding at a corner of the end (right end in FIG. 74B) of the base portion 26 is held in the long elongated hole such that it is movable longitudinally (axially of the tilt rotary shaft 15 and up/down in FIG. 74).
According to the above-mentioned configuration disclosed in DE 10 246 432 A1, the power roller 8a moves only in the axial direction shown by an arrow (a) in FIG. 75A by axial movement of the input- and output-side inner faces 3, 7, the axial sides of the input and output discs 1, 6. As the power roller 8a moves in the direction of arrow (a), the guide rod 32 moves axially of the tilt rotary shaft 15 in the long elongated hole in the direction of arrow (b) in FIG. 75B. According to this configuration, the arc motion due to the eccentric amount δ2 between the central axes X29 and X30 of the crank member 29 and the circular hole 30 and the arc motion due to the eccentric amount δ1 between the central axes X26 and X27 of the base portion 26 and the support shaft portion are offset. As a result, the support shaft portion moves linearly.
Similarly, according to the first configuration in the related art shown in FIG. 70 and the second configuration in the related art shown in FIGS. 71 to 75, the contact between the outsides of the power rollers 8 and the discs 1, 1a, 1b, 6 is appropriately maintained regardless of the amount of elastic deformation of the members by moving the power rollers 8, 8a axially of the discs 1, 1a, 1b, 6. In any configuration, however, the structure for moving axially the power rollers 8 is complicated, so that manufacturing and managing, and assembling of parts are complicated and the cost increases accordingly. According to the configuration disclosed in JP-A-2003-294099, a direct-operated rolling bearing is disposed between the inner surface of a trunnion and an outer ring of a thrust ball bearing for rotatably supporting a power roller, so that each disc of the power roller is allowed to move axially. However, the above problems appear in the configuration disclosed in JP-A-2003-294099.